低渗透油藏水驱采收率影响因素分析

FACTORS EFFECTING THE WATER FLOODING RECOVERY IN LOW PERMEABLE RESERVOIRS

实验表明， 低渗透油藏具有启动压力梯度， 因此其渗流规律与中、高渗透油藏不同。通过对低渗透油藏中注水井排和采油井排的定压水驱进行数值模拟， 分析了低渗透油藏水驱采收率的影响因素， 包括多孔介质孔隙结构、油水相对渗透率曲线、启动压力梯度、注入速度和注采井距。分析表明， 低渗透油藏的水驱采收率受到启动压力梯度的影响， 启动压力梯度越大， 见水时间越早， 产油量和产液量越小， 阶段采出程度、无水采收率和水驱采收率越低； 而增大生产压力梯度， 可以有效地降低启动压力梯度的影响， 生产压力梯度越大， 见水时间越早， 产油量和产液量越大， 阶段采出程度、无水采收率和水驱采收率越高； 增大生产压力梯度的方法有增大注入量和减小注采井距两种， 都可以提高低渗透油田的开发效果。

Experiments show that a low permeable reservoir has a starting pressure gradient, and therefore different seepage rule from that of middle and high permeable reservoirs. This paper performs an numerical modelling on constant water flooding of water injection well arrays and production well arrays in low permeable reservoirs and analyses the factors effecting the recovery of water flooding in low permeable reservoirs, including pore structure of porous medium, oil water relative permeability curve, starting pressure gradient, injection rate and injection production well spacing. Analysis indicates that the water flooding recovery of low permeable reservoirs is effected by starting pressure gradient. The larger the production pressure gradient is, the earlier the water breakthrough is, the more oil production and fluid production is, and the higher the episode recovery percent , water free recovery and water flooding recovery are. The methods of increasing production pressure gradient are increasing injection rate and decreasing injection production well spacing, both of which can improve the development effect of low permeable oil fields.